Of the 2423 Kepler candidates yet to be confirmed, there’s one that is of symbolic importance: Kepler-1658 — Kepler’s first find.

Ten years after being spotted by the Kepler Space Telescope, KOI 4.01, the very first exoplanet candidate, has been confirmed

Kepler’s First Object of Interest is a Planet

KOI 4.01 orbits a star called KOI 4, or Kepler Object of Interest 4 — KOI 1, 2, and 3 were discovered before the Kepler mission.

Astronomers initial estimates of the size of KOI 4.01 and KOI 4 were way off.

KOI 4 star was first thought to be 1.1 times the width of the Sun, and KOI 4.01 categorized as a Neptune-sized planet.

Then, Kepler detected a “secondary eclipse”, or a second drop in light as the object passed behind its star. If the world was as small as Neptune, the team wouldn’t have been able to detect its second dip. So KOI 4.01 was dismissed as a false positive.

Now, an international team of astronomers has confirmed that KOI 4.01 is indeed an exoplanet. Furthermore, both it and its home star are about three times larger than previously thought.

Team leader Ashley Chontos, a graduate student at the University of Hawaii in Honolulu, presented the results of the study on March 5 at the fifth Kepler/K2 Science Conference.

Chontos and her colleagues revisited KOI 4.01’s data using a combination of asteroseismology and spectroscopy to analyze stellar sound waves.

“Our new analysis, which uses stellar sound waves observed in the Kepler data to characterize the host star, demonstrated that the star is in fact three times larger than previously thought. This in turn means that the planet is three times larger, revealing that Kepler-1658 b is actually a hot Jupiter-like planet,” said Chontos.